I believe that there'll be pressure to get Avengers back in theaters as quickly as possible --- i.e., 2015. Face it: 2013 and 2014 are going to be characterized by post-Avengers letdown (there's no way in hell that Ant-Man, GOTG, or the sequels to Iron Man, Cap and Thor are going to generate box office numbers even close to Avengers), so by the time 2015 rolls around, the cries for "where's Avengers 2?!?!?" are going to be pretty deafening, and Marvel Studios risks missing the boat if they put it off for another year of solo films that generate half (or less) the revenue that Avengers 2 would.